Western azalea
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Western azalea ( Rhododendron occidentale ) |
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The western azalea ( Rhododendron occidentale ) is a shrub or tree belonging to the genus Rhododendron . The white to pink-flowered species occurs in western North America. It came into culture as early as 1850 and was crossed with a large number of well-known rhododendron varieties .
description
The western azalea is a deciduous shrub or tree that reaches heights of up to 8 meters, in extreme cases up to 10 meters. The bark is smooth or vertically furrowed and fibrous. The twigs are dense or irregularly hairy or completely bare.
root
The species can thrive in very humid habitats, even in places where the roots are practically in the water. In such moist places, the root system is very compact and does not measure more than 1.80 meters in depth and diameter. In drier places, the root system is also compact, but is supplemented by one or more tap roots that penetrate deep into the soil.
leaves
The leaves sit on glandular or hairy petioles. The leaf blades are ovate, inverted ovate or elliptical and between 3.5 and 8.2 inches long and 1.2 to 2.9 inches wide. They are thin and cuticle-like with entire, ciliate or glandless-hairy, rarely with a glandular-hairy edge. The tip of the leaf is sharpened or rounded and often prickly. The midrib is protruding. The underside of the spread is smooth or irregularly haired, often with glandular hair. The upper side of the leaf is thinly covered with glandular or glandular leaf hairs or else completely bare.
blossoms
The flower buds are isolated or densely hairy, ciliate or ciliate and glandular at the edge of the scales. The inflorescence consists of 3 to 15 flowers . The bracts resemble the bud scales. The flower stalks are between 9 and 26 millimeters long, they are hairy and glandular or rarely non-glandular.
The flowers open with the leaves, they stand upright or horizontally. They smell pleasant or extremely unpleasant. The five sepals are fused, the sepals are between 1 and 4 millimeters long and hairy glandular or non-glandular.
The funnel-shaped flowers of the western azalea are extremely variable in terms of color. Possible colors of the crown are: white with a yellow spot, white and pink or salmon-colored, pink with an orange spot, color gradients from white to red on the tube, or more rarely white with yellow stripes. They measure 30 to 58 millimeters and have glandular or non-glandular hair on the inside and outside, and bald on the outside. The petals are fused and the corolla lobes measure 13 to 29 millimeters. The widening tube is 15 to 29 millimeters long, it is as long as the corolla lobes or longer. Because of the relatively long flower tube, the western azalea cannot be pollinated by all insects, but the New World hawk-line Hyles lineata is a reliable pollinator .
The five stamens are unequal and protrude far from the flower. They are between 40 and 75 millimeters long.
fruit
The capsule fruits are formed on upright stems and measure between 12 and 22 millimeters in length and 4 to 14 millimeters in width. They are hairy or non-glandular. The seeds are not clearly winged. The seed coat is thickened at the two flattened ends of the seed.
Chromosome number
The number of chromosomes is 2n = 26.
Distribution and location
The natural range is in California and Oregon , as well as in the extreme north of Lower California . It inhabits the Cascade Range , the Klamath Mountains and the California Coast Mountains . In California, the western azalea is common in the Sierra Nevada and Peninsular Ranges . There are smaller deposits on the Bay of San Francisco . The northernmost occurrence is near Bandon (Oregon) , the southernmost on Palomar Mountain in Mexico.
The western azalea thrives on moist, wooded slopes and on the bottom of canyons , on river banks, on ridges and in thickets, in swamps and on the Pacific cliffs at altitudes between 0 and 2,700 meters. It likes to grow in association with the cobra lily ( Darlingtonia californica ) and the California lady's slipper ( Cypripedium californicum ). Also with Lilium pardalinum subsp. pitkinense lives the species together.
ingredients
Like all rhododendron species, the western azalea also contains grayanotoxins , especially grayanotoxin I (Acetylandromedol), which is highly toxic to humans.
Systematics
Within the genus rhododendron the type in which is section Pentanthera , subsection Pentanthera that a total of 14 types contains, placed.
A 1977 study of the flavonoids in the leaves of 18 North American rhododendron species found that the western azalea's closest relatives are Rhododendron austrinum and the Pontic azalea ( Rhododendron luteum ). A broader molecular genetic study of RNA - polymerase RPB1 in 2005 took into account a total of 87 rhododendron species. One result was that the Pentanthera section is paraphyletic . The closest relative of the western azalea was found to be Rhododendron canescens . In this work, too, there was a close relationship to the Pontic azalea ( Rhododendron luteum ). Rhododendron austrinum was not one of the species studied. Another work from 2000, which examines the relationship within the Pentanthera section using ITS sequences, once again confirms the close relationship to Rhododendron luteum .
The species is divided into three varieties :
- Rhododendron occidentale var. Occidentale , the nominotypical taxon
- Rhododendron occidentale var. Paludosum Jeps.
- Rhododendron occidentale var. Sonomense Rehder
Culture
The western azalea was discovered by Frederick William Beechey in 1827 and then collected by David Douglas , Karl Theodor Hartweg, and Joseph Burke II . William Lobb sent the first seeds to England to Veitch Nurseries in 1850 , where the species first bloomed in 1857. The first hybrids were bred by Anthony Waterer in the 1870s.
M. Koster & Sons already crossed the western azalea with hybrids from the Japanese azalea ( Rhododendron molle ) in 1895 .
The first monograph on the species was written by Leonard Frisbie in the 1950s and published in 1961.
Significant hybrids are:
- 'Delicatissimum' - ( Koster ) with creamy white and pink overflowing flowers with a yellow spot, which are fragrant.
- 'Exquisitum' - (Koster, 1901) with crinkled, whitish-pink flowers with an orange-yellow blotch that have a strong scent.
- 'Irene Koster' - (Koster) late flowering variety with pink flowers with a small spot.
- 'Magnificum' - (Koster, 1910) with purple-red flowers and a golden-yellow spot.
- 'Summer Fragrance' - ( R. occidentale × luteum , Pratt , 1963) light yellow with a strong yellow spot.
They all received the RHS Award of Garden Merit in 1993.
literature
- Gordon C. Tucker: Rhododendron occidentale . In: Flora of North America . tape 8 . Oxford University Press, Oxford 2009, ISBN 978-0-19-534026-6 , pp. 467 ( online [accessed December 28, 2009]).
- Frank Mossman: The Western Azalea, Rhododendron occidentale . In: Quaterly Bulletin of the American Rhododendron Society . tape 28 , no. April 2 , 1974 ( online [accessed December 30, 2009]).
- Gary D. Wallace: Rhododendron occidentale . In: James C. Hickman (Ed.): The Jepson Manual. Higher Plants of California . University of California Press, Berkeley 1993, ISBN 978-0-520-08255-7 ( online [accessed December 28, 2009]).
Individual evidence
- ^ Frank D. Mossman, Britt M. Smith: Rhododendron occidentale - One Species or Many? In: Quarterly Bulletin of the American Rhododendron Society . tape 23 , no. July 3 , 1969 ( online [accessed January 4, 2010]).
- ^ Verne Grant: The Systematic and Geographical Distribution of Hawkmoth Flowers in the Temperate North American Flora . In: Botanical Gazette . tape 144 , no. 3 , September 1983, p. 439-449 , JSTOR : 2474443 .
- ↑ Bruce L. King: The Flavonoids of the Deciduous Rhododendron of North America (Ericaceae) . In: American Journal of Botany . tape 64 , no. 3 , March 1977, p. 350-360 , JSTOR : 2441979 .
- ↑ Loretta Goetsch, Andrew J. Eckert, Benjamin D. Hall: The Molecular Systematics of Rhododendron (Ericaceae): A Phylogeny Based Upon RPB2 Gene Sequences . In: Systematic Botany . tape 30 , no. 3 , 2005, p. 616–626 ( online [PDF]).
- ↑ SM Scheiber, RL Jarret, Carol D. Robacker, Melanie Newman: Genetic relationships within Rhododendron L. section Pentanthera G. Don based on sequences of the internal transcribed spacer (ITS) region . In: Scientia Horticulturae . tape 85 , no. 1-2 , July 2000, pp. 123-135 , doi : 10.1016 / S0304-4238 (99) 00142-9 .
- ↑ Rhododendron occidentale. In: The Calflora Database. Retrieved December 29, 2009 .
- ^ Frank D. Mossman, Britt Smith: Further Trips to the Rhododendron Occidentale Patches . In: Quarterly Bulletin of the American Rhododendron Society . tape 22 , no. July 3 , 1968 ( online [accessed December 29, 2009]).
- ↑ Rhododendron occidentale. In: Landscape Plants. Images, Identification, and Information. Oregon State University, accessed December 29, 2009 (Volume 3).
- ^ Leonard Frisbie: Rhododendron occidentals survey . In: Rhododendron . January 1961.
